This invention is directed to a motor control system and more particularly to a motor control system for developing full load torque with motors which exhibit high resistance. In attempting to apply variable speed inverters, (i.e., converters of DC to AC) to fractional horsepower 3.phi. AC induction motors (i.e., less than 1 HP), it has been found that the motor would tend to stall out at low speeds while attempting to provide full load torque, whereas high horsepower motors (e.g., 1 HP and up) would not encounter such difficulties.
In studying the problem, it was discovered that fractional horsepower motors exhibit a high resistance. In comparison with high horsepower motors. Accordingly, in order to be able to utilize inverters in a manner that full load torque and current could be provided over the entire speed range, it was necessary to overcome the peculiarity of high resistance apparently common to fractional horsepower motors. The present invention solves the foregoing problem by creating an offset voltage in a non-linear fashion to provide constant torque over the entire speed range of the control system.